opalescent my DC3 doesn't sleep - I'm not going to say anything about phases because for us it isn't, or at least its a 23 months and counting phase, but about the coping...
Don't look at the clock during the night, at all and don't count the wake ups - that way madness lies. Have an alarm set for morning even if you know you're 99% likely to be up then, rather than constantly looking at the clock to see if it is.
If you ever can sleep when DC does, then do (I know people say this and in real life it is often totally impractical for a myriad of reasons, like older siblings or naps only lasting 30 minutes)
If it goes on longer and you feel you can't cope, try co-sleeping (taking sensible safety precautions, which you can google or ask on here about) - it is the solution for some people, though it doesn't work for everyone.
If you possibly can, get your partner to do a night at the weekend/ before a non work day, and to give you a lie in on the other weekend/ non work day - it makes a difference. My DH gets up with my kids on Sunday mornings and it is the only 4 hour stretch of sleep I get - it is a life saver.
Accept that the other brave, stoical natural mothers are acting in many cases - loads of people are just staggering by in the early years, but for most people the answer is sticking on a smile and continuing to go to toddlers/ meet for coffee and try to chat about other things, as if you let yourself collapse its hard to get back up again.
I hate the "this too shall pass" thing as it sounds smug, and not everything does - but in the case of non sleeping babies and toddlers, it will, eventually, nothing stays the same for ever.